Abstract

Elemental identification at single atom level has been achieved with a low temperature scanning tunneling microscope. Magnetic atoms (Mn or Cr) adsorbed on a superconductingPb substrate induce a set of well-defined resonance states inside the superconductor gap in scanning tunnelingspectroscopy. We show that these localized characteristic bound states could serve as fingerprint for chemical identification of the corresponding atoms, similar to atomic/molecular spectra widely used in optical spectrometry. The experiment demonstrates a technique for element-resolved spectroscopy with simultaneous atomic-level spatial resolution. The influence of magnetic impurity concentration on the bound states has also been investigated.